This invention relates generally to eddy current probes and, more particularly, to methods and apparatus for sealing eddy current transducer components within an eddy current probe.
Eddy current (EC) inspection devices may be used to detect abnormalities and/or defects in a component, such as a rotating machinery component. At least one known EC inspection device is used to detect a distance to a shaft during rotation. If a relatively large variation is detected, an alarm signal is activated. Other known EC inspection devices are used to detect cracks, pings, dings, raised material, and/or other surface imperfections on a surface of the component, and/or to evaluate material properties of the component including the conductivity, density, and/or degrees of heat treatment of the component.
During operation, known EC devices measure the interaction between an electromagnetic field generated by the EC device and the component being tested. For example, known EC devices include a sensing coil that generates a magnetic field. When the sensing coil is positioned adjacent to a conductive component, an eddy current is generated on the surface of the component. A flaw on and/or near the surface of the component generates a disruption in the eddy current field, which produces a secondary magnetic field that is detected by the sensing coil. The secondary magnetic field is converted into an electrical signal that is transmitted to a strip chart recorder, for example, and recorded.
An eddy current probe typically includes a tip assembly, a probe cable and a probe case. The tip assembly packages a sensing coil that is electrically interfaced with or coupled to the probe cable. Typically, a single O-ring seal is positioned at the interface to prevent or limit undesirable liquid leakage into the tip assembly and/or the probe case at the interface. Known EC inspection devices for underwater applications may also include a swage-type fitting that sealingly couples a protective tube about the probe cable and to the probe case to prevent or limit undesirable exposure of the tip assembly and the probe case to a pressurized liquid environment.
While inspecting rotating machinery components in pressurized liquid applications, pressurized liquid, such as water or a lubricant, may enter into the tip assembly and undesirable contact the sensing coil of an eddy current transducer. The liquid may enter through the probe case and into the tip assembly and/or liquid may enter into the probe cable through openings defined in the probe cable.